I have a number of ESP8266 projects. These have all been building and deploying wonderfully under the previous version of PIO.

Got prompted to update on Friday. The moment the update completed the agony began - none of my projects would compile anymore. Have been tearing out my hair all weekend

Specifics - using ESPAsyncUDP, ESPAsyncTCP, ESPAsync web server etc on a Windows 10 PIO environment, customised to use github arduino/ESP8266 core. NOTE: it took some time to set up the environment, but all projects were building perfectly.

Tried complete removal of PIO and Atom and fresh install, re-did all my steps to download latest version of libraries, github version of ESP8266 Arduino core, tried all the platformio.ini tweaks. Nothing.

So, tried the most basic test:

Install from fresh (full delete and clean of all Atom/PIO data and directories, set up new project in fresh directory etc

i have just installed the latest platformIO, and i think both espressiv8266_stage and espressiv8266… somehow when i try building with esspresiv8266 it works, and with esspresiv8266_stage i face this problem… is there something else that needs to be done?
i just followed the description on the doc page you posted

Aahhh sorry, i had to post back the details here, but was running behind schedule and missed it
It is all working fine now Somehow, with the 2.x version it was successfully finding and using my libraries from the Arduino Folder using the lib_dirs var in the .ini file. With the new version this somehow didn’t work.
So eventually i ended up copying all necessary libraries to the /lib folder of the project.
Also before this my project was Arduino-style (with the sketch named XXX, staying in a folder XXX), this i also changed and now my sketch is in /src folder but renamed it to .ino.

Somehow i couldn\t find a combination of the library dependency filter that works for the project in it’s old style.

Anyway i had planned this refactoring quite some time ago as there were too many dependecies, and now everything is fine and i am happy with it. The build output of the PIO 3 is much cleaner and apparently also faster